In rotors of steam turbines, local thermal stresses arise during running up and running down of the turbines, which are caused by the rapid change of the hot gas flows. Such stresses arise particularly in the region of the steam inlet of the high-pressure and intermediate-pressure steam turbines and often lead to crack developments in the region of the blade grooves, especially of the first blade rows. These can limit the operational service life of the rotor and particularly the number of risk-free running up operations of the turbine.
DE 2423036 discloses a turbine rotor disk with grooves which extend radially inwards between adjacent blades. The grooves serve for avoiding circumferential stresses on the edges of the rotor disks, which can arise on account of the thermal expansion of the rotor. On the base of each groove, a drilled hole is located in each case, into which a rivet is inserted.
EP 1724437 discloses a steam turbine with a fastening region for the rotor blades on the turbine rotor, the radial distance of which fastening region from the rotor axis reduces in the direction of the axial rotor blade thrust. Between the fastening region of the rotor blades and the equalizing piston, the rotor has a continuous recess (28) over the rotor periphery, which ensures an entry of steam from the inflow chamber in the inner casing to the equalizing piston and at the same time acts as a relief notch for the initial rotor blade thrust.